How does the CMS bolt load cell work?
The BoltSafe bolt load cell is a specially designed load cell (load sensor) that monitors the actual bolt load in bolted joints. CMS stands for Continuous Monitoring System, which allows for continuous monitoring of the bolt load from one connection point. Several load sensors can be interconnected within a network. Using a BoltSafe load cell eliminates any uncertainties about the bolt load. This results in enhanced safety, dependable joints and better control over the structure. Besides those safety benefits, the costs during installation and throughout the joint’s service life are reduced.
Each sensor utilizes an ASIC (Application Specific Integrated Circuit), which performs all signal conditioning and digital communication. Because of this, each BoltSafe load sensor has a unique serial number for individual identification and traceability. The digital monitoring system not only measures the bolt load, but can also monitor the sensor temperature. The load cell is available in two kinds of steel: our regular stainless steel, and a stronger version that can withstand 15% more load while keeping the same compact dimensions.
Another application of the load cells is in temporary construction or for Structural Health Monitoring. In this case the sensors are used as washers to check the load in the construction to make sure that the (temporary) construction does not collapse.
How is the CMS bolt load cell used?
The load cell is shaped and used as a regular washer and is available in sizes M12 to M72 and 7/8” to 2-3/4”. Sensors for bolt sizes smaller than M12 and 3/4”are available upon request. The BoltSafe bolt load cell is installed on the non-driven side of a bolted connection, preferably under a nut. While tightening the bolt, force is being applied to the load washer, which will result in minor deformation of the stainless steel washer. The sensor constantly measures changes in electrical resistance caused by these deformations. This data is used to determine the actual bolt load at any given moment.
Because of the rugged design of the load cells, they are able to withstand harsh conditions, such as heavy industrial environments. The load sensors can be used in contact with oil, rain, seawater, ice and temperatures up to 80 degrees Celsius. We do not recommend using the washers in conditions where the temperature is above 80 or below -40 degrees Celsius.
The calibration of the sensor is done once by BoltSafe. After that, the sensor is plug-and-play and there is no need to recalibrate when different readout methods are used. There is also no need for recalibrating the load cell during its service life, provided that it is used according to its specifications and requirements.
Contact us for more information or to order our CMS bolt load cells
Benefits of a continuous monitoring load cell
With continuous monitoring, it is a lot easier to determine the bolt load while the load cell is mounted, at any time. In addition to checking the bolt load at any given time, it is also possible to view historical data. This helps to determine when and where a problem with the bolt load might have occurred. The CMS sensor is usually slightly smaller than the PMS sensor. Another benefit of the CMS load cell is that it can be linked with other CMS load cells in a network, where data from all sensors can be monitored at once. The live data from the bolt load cells can be checked remotely with different readout methods.
View historical data
Link other CMS sensors
Check live data remotely
Readout methods that are compatible with the CMS bolt load cell
The CMS load cell data can be read by various readout systems. The first option is our handheld reader. This is used to quickly see the bolt load of the currently connected sensor and is used with a cable connection. The second method is Network with PDI (CM-1000 box with PDI), where you can monitor and log multiple sensors at once linked to a Windows PC. Our CMS load sensors have a cable installed for the purpose of interconnecting several sensors into a network. This way, the residual bolt load can be continuously monitored from one connection point. The next method is Network with PDI-NT (CM-1000 box with PDI-NT). This is a standalone system for monitoring and logging multiple load cells at once without the need for a PC, because it has its own display. Both network methods allow for linking eight sensors per network box and linking 32 network boxes together. This means that it is possible to monitor the bolt load from a maximum of 256 CMS sensors at once.
Another method is the RS-232 and Analog Converter. This acquires data from one sensor at the time and is able to convert BoltSafe data to various analog outputs. The converter can be linked to a PC where the data can be read. An important feature of this converter is that it is equipped with a relay, which can be used as an alarm to give a signal when a minimal bolt load is reached, for instance. The last possible readout method is our newest innovation, the IoT-node. IoT stands for Internet of Things. We use the LoRaWAN technology which stands for Long Range Wide Area Network. This IoT-node sends out a signal to a cloud network server, which enables remote readout of the data. A device with an internet connection is all that is needed to acquire the bolt load data. One IoT-node is required for every bolt load cell sensor.